Applying menthol to tobacco in a pneumatic system



United States Patent [72] Inventors Robert L. Key, 11!; [56] ReferencesCited Melvin C h y. Durham, N.C. UNITED STATES PATENTS g gz' gr 19682,063,014 12/1936 Allen 1 31 |7x 5] Patented ai 3,026,881 3/1962 Canan.131/144 73] A M m ed 3,357,436 12/1967 Wright 131/136X i ,j W 3,419,01512/1968 Wochnowskt 131/138 FOREIGN PATENTS 135,805 3/1961 USSR 131/138Primary Examiner-Samuel Koren Assistant Examiner-James H. CzenvonkyAttorney- Kenyon and Kenyon, Reilly, Carr & Chapin [54] APPLYING J 2 32To TOBACCOINA ABSTRACT: A method for the continuous application of'NEUMA-ncs I. 1 menthol additives to tobacco. Tobacco is injected intoand cmsnnw pneumatically conveyed in a conduit. A menthol solution is[51] [1,3, (L 131/144, then injected into the conduit at a pointdownstream from the 131/136 injection of the tobacco into the conduit.For example, in a [51] In, A241) 03/12 pneumatic system tobacco is blownthrough a conduit and [$0] I'HdofSarch 131/136, blended with mentholupon passage through a venturi com nected with a supply of menthol.

APPLYING MENTI'IOL TO TOBACCO IN A PNEUMATIC SYSTEM BACKGROUND Theaddition of flavorants or aromatic compounds such as menthol to tobaccopresents several problems. Conventional methods for the application ofadditives to tobacco include direct mixing, spraying, tumbling andvariations thereof. It is impractical to mix menthol directly withtobacco since it is too difficult to control the very minor quantitieswhich it is desired to use. The spraying of a dilute menthol solutiononto tobacco must be carefully controlled to obtain a sufficient andaccurate amount of menthol-addition. The spraying of menthol onto atobacco conveying belt does not result in adequate or uniform retentionof the menthol, particularly if ambient conditions are not carefullycontrolled. Therefore, attempts have been made to carry out the sprayingin closed vessels which conserve and contain volatile components. Theapparatus may comprise a cylinder into which menthol is sprayed as thetobacco istumbled about by rotationof the cylinder or by movement ofagitator blades within the'cylinder. Considerable periods of time areoften requiredto insure thorough and homogeneous blending in thisfashion. Moreover, this type of outside the building by exhaust fans.However, these commercial methods for accomplishing the addition ofmenthol to tobacco have not been entirely satisfactory. There is a needfor a method of adding menthol which is both accurate as to the amountof menthol retained on the tobacco and capable of being integrated intoacontinuous operation.

It is therefore an object of the present invention to provide .animproved method for the blending of tobacco and tobacco additives.

THE INVENTION This invention is directed to a method and means formixing tobacco with a flavorant or aromatic compound in liquid form orin solution. The tobacco is blown through a conduit which is incommunication with a source of an additive, such as menthol in analcohol solution. The menthol is preferably supplied to the conduit ,ata reduced portion thereof, or throat, where the venturi effect draws thementhol solution into the. conduit and disperses it onto the tobacco.

The apparatus of this invention is designed for continuous and uniformmentholation of tobacco in a pneumatic system, preferably withthementhol in an ethanol solution. The unit consists of a hopper tocontinuouslyfeed tobacco into the feed inlet of the conduit where it ismixed with an air stream. This tobacco-airmixture passes through aventuri and is combined with the ethanol-menthol mixture which isintroduced at the throat of the venturi. The tobacco is separated fromthe air stream by a cyclone collector. The tobacco can then be furtherprocessed and the air stream recirculated.

This invention will be illustrated in greater detail by the followingexamples in conjunction with the attached FIGS.

FIG. 1 shows a preferred embodiment of this invention.

FIGS. 2 and 3 disclose alternative configurations for adding menthol totobacco.

The system is designed to pneumatically feed cut blend tobacco into aconduit, where it is continuously contacted with the menthol-ethanolsolution. A constant level of menthol canbeapplied to tobacco in.this-manner.

In FIG. 1 air is delivered to conduit 1 from blower motor 2. The cutblended tobaccois drawn from a storage bin 3 and delivered by a conveyorbelt 4 into hopper or loading chute 5. The tobacco is picked up byrotary valve 6 and fed into a standard feed inlet section of conduit 1having a baffle 7 slightly upstream from the feed inlet. The continuousair stream flowing across the bafile creates'a negative pressure at thefeed point. The tobacco is carried along and dispersed by the airstreamthrough the conduit. The menthol-ethanol solution is fed into thethroat of venturi section 8 from spray nozzle 9. The menthol deliverysystem, which is not shown, may comprise conventional liquid pumpingmeans and an air pressure supply of, for example, 10 p.s.i.g. Thementhol solution, from conduit 10, and the air, from conduit 11,converge in head 12. The spray nozzle 9 provides an atomized mentholsolution which is mixed with the air-tobacco stream. The stream thenpasses into cyclone collector 13 from which the tobacco exits throughrotary valve 14. The air stream passes upward through conduit 15 andback to blower 2.'

In a further embodiment, an additional venturi (not shown) maybepositioned between baffle 7. and venturi 8; this additional venturi mayfurther disperse the tobacco into the air current and breaks up anywads.

' EXAMPLES 1-13 Tobacco was treated with a menthol solution in anapparatus similar to that of FIG. 1. Instead of recirculating the airthrough conduit 15, the air was drawn off through conduit 16 and passedthrough a water-cooled condenser. The condensate was analyzed and theamount of menthol actually applied to the tobacco was determined. Theresults are set for in Table I, with the operating data for each of theexamples. The menthol application efficiency ranged from 54.1 percent to63.4 percent.

TABLE I Example Inlet air pressure, p.s.i.g ,15. 0 14. 0 15. Inlet airvolume, c.i.m 20. 0 19. 5 19. Wt. tob. treated, gm.... 293 540 1, 56Treatment time, min 1. 5 1.5 3. Menthol sol. feed rate, ml./min 7.0 8. 28. Tobacco throughput rate, gm./rnin 360 44 Menthol available, gm 2.0 2.4 6. Theoretical menthol appln., percent by wt 0. 68 0. 44 0.3 Actualmenthol appln., percent by wt 0.37 0.26 0.2 Application efiiciency,percent", 54. 1 59. 7 63. 4

EXAMPLES 4-6 In order to determine the optimum feed point forintroducing menthol solution into'the pneumatic system, a series of runswas madewith menthol fed into the system upstream of the tobacco inletpoint.

In accordance with the apparatus of FIG. 2, the menthol solution wasintroduced at. 17 into the throat of a venturi,-'118,

located upstream of the cut tobacco inlet point 19. Tobacco enteredthrough a rotary valve (not shown) and was drawn into the system bynegative pressure below the valve. The negative pressure is created byair passing beneath a baffle plate 20. The menthol solution injectedupstream of the tobacco was not well dispersed in the air stream and didnot give a 1 uniform application. As the solution entered the airstream,-.

ethanol evaporation caused cooling and thereby brought about thecrystallization .of menthol prior to contacting the tobacco downstream;Only 0.03' percent to 1.08 percent menthol was deposited upon thetobacco.

eliminated the menthol crystallization; however, 'b'nly =l5.7

percent of the menthol was deposited'upon the tobaccoe The data forth isrun is set forth in Example 4 of Table II.

TABLE II Inlet air pressure, p.s.i.g Inlet air volume, elm... \\t. loh.treated, gm.. Treatment time, min .\lenthol solution iced rate, inlJminTobacco throughput rate, gm./min Menthol available, gm Theoreticalmenthol appln., percent by wt Actual menthol appln., percent by wtApplication efliciency, percent FIG. 3 illustrates another variation ofthe method of introducing menthol. The method feed mixture wasintroduced into a copper tube 21 positioned directly behind the tobaccoinlet baffle 22. The results of this method are set forth in Examples 5and 6, Table ll; only 19.2 percent to 28.5 percent of the availablementhol was adsorbed on the tobacco.

EXAMPLE 7 in the operation of a plant unit for pneumatically conveyingand mentholating cut tobacco, a closed-loop recirculation system wasused in accordance with the apparatus of FIG. 1. Air for the unit wassupplied by an 800 cfm all aluminum, sparloproof blower. The air fromthis blower was passed through a 2% inch throat diameter venturi,creating a negative pressure at the throat where cut tobacco enteredthrough a rotary valve. The cut tobacco was fed from a conveyor beltfeeder regulated by a weigh belt, and capable of controlling from 300 to900 pounds of tobacco per hour. Atomized menthol solution was nextcontacted with the tobacco and mixed via a second venturi downstream,with a 3 inch diameter throat about 6 feet downstream. To insuresufficient contact time, the tobacco was conveyed through 25 feet ofstraight 6 inch duct before entering a cyclone separator. After thetobacco was separated in the cyclone, it exited through a rotary valveat the bottom. The air leaving the top of cyclone was recycled to theblower intake through an 8 inch return duct.

in the interest of safety a portable combustible gas indicator (notshown) was used to monitor ethanol content and indicate weight with thebalance being mostly ethanol plus lesser amounts of water and flavoring.The menthol solution was applied at a rate of 987 ml/l 00 pounds oftobacco. At a tobacco throughput rate of 700 pounds/hr. an efiiciency of93.3 percent was recorded; for 900 pounds/hr. the efficiency was 92.8percent. An advantage of higher throughput rates is that the tobaccofilling power is slightly improved.

EXAMPLES 8-16 The advantages of the above methods and means were shownin the following examples by the adsorption of menthol on cut blendtobacco in a closed air recirculation system. The menthol and tobaccowere introduced into a 1.28 cubic foot plexiglass box equipped with anelectrically heated air recirculation system. The parameters checkedwere temperature (wet and dry bulb), relative humidity, and contact timeof the tobacco in the menthol atmosphere. The menthol concentratio n inthe enclosed chamber and the temperature at which the tobacco wascontacted with the menthol;saturated atmosphere were varied within thestated limits shown in Table III.

A typical menthol concentration check was made as follows: a watch glasscontaining menthol was placed in the bottom of the chamber and the topwas secured; air circulation was begun through the chamber; the air wasdriven by a blower through a heated copper tube into the chamber andback to the blower; when the desired air temperature inside the chamberwas reached, a sample was taken of the atmosphere inside the chamberwith a syringe for menthol determination.

in order to determine the amount of menthol condensed or adsorbed on cutblend tobacco, 8.5 grams of tobacco were weighed into an open-top, wiremesh cylinder 1% inches in diameter and 6 inches high. The cylinder wasplaced inside the chamber for retention times from 2 to seconds. Therecirculating, menthol-saturated air was passed over the sample for thedesired length of time while a sample of the atmosphere was collectedand wet and dry bulb temperatures recorded. The tobacco sample wasremoved and analyzed for menthol determination. During a portion of theruns, steam was injected into the chamber to test the effect of relativehumidity with respect to the amount of menthol deposited upon tobacco.The results of these runs are shown in Table 111.

TABLE III Menthol Menthol deposited eoncen- Menthol on tobacco ContactWet Percent tration percent percent time 01 bulb relative in air, by wt.by wet tobacco temp. humidity mgm./ml. in air wt. basis in sees.

83 16 8. 9X10- 008 .014 15 90 22 13. 8X10- 012 008 45 94 25 15. 4 10-013 006 30 93 24 11. 6 10- 010 012 60 118 34 46.0X10- 039 .010 10 123 4053. 2X10- 045 014 5 148 75 71. 8 1Ct- 061 015 15 146 62 98. 4 10- 084022 30 148 66 96. 8X10" 082 .013 2 magnitudes in terms of percent of thelower explosive limit. The system was maintained at or below 80 percentof the lower explosive limit of ethanol at all times. To accomplish thisthe system was vented to the atmosphere through the outlet located justabove the cyclone as necessary.

Blended tobacco w: continuously fed into the system at 500 pounds perhour. The tobacco was conveyed by an air stream moving at about 325cubic feet per minute. As the tobacco passed through a venturidownstream it was contacted by menthol solution sprayed into the throatof the venturi. The sprayed solution contained 19.8 percent menthol byThe highest percentage menthol deposited on a tobacco sample was 0.0217percent by weight of wet tobacco. This occurred at higher temperature(164 F.), high relative humidity (62 percent), and 30 seconds contacttime. The menthol collected on the tobacco was only 7 percent of thetarget, which was 0.35 percent by weight (wet basis). The hightemperatures which would be necessary to increase the concentration makethis method unfeasible for mentholation of cut blend tobacco. Theresults indicate that this method is not conducive to mentholapplication to tobacco because only a small amount of the menthol neededwas adsorbed on the tobacco and the temperature needed to increasementhol concentration to an acceptable level would be well in excess of200" F. and, therefore could not be adapted to tobacco processing.

In summary, the method of this invention is basedon the principle ofdispersing menthol in an ethanol solution into an air stream throughwhich cut tobacco is being pneumatically conveyed. By regulating theamount of menthol solution, the tobacco feed rate as tobacco enters thesystem, and the contact time, the desired level of menthol can beapplied to the tobacco. After the tobacco has been treated, it isremoved from the system via a cyclone collector. The air containing theremaining volatiles is preferably recycled back into the system.

This invention has been described in terms of specific embodiments setforth in detail. Alternative embodiments will be apparent to thoseskilled in the art in view of this disclosure, and accordingly suchmodifications are to be contemplated within the spirit of the inventionas disclosed and claimed herein.

lclaim:

l. The method of treating tobacco which comprises:

a. injecting tobacco into a conduit;

b. pneumatically conveying said tobacco through said conduit; and

c. injecting a menthol solution into said conduit at a point downstreamfrom said injection of said tobacco into said conduit.

2. The method of treating tobacco which comprises:

a. driving air through a conduit;

b. injecting tobacco into and dispersing it in said conduit;

c. injecting a menthol solution into and dispersing it in said conduitin contact with said tobacco, wherein said step of injecting the mentholsolution is carried out downstream from the injecting of said tobacco;

d. separating said tobacco from said air; and

e. recirculating said air through said conduit.

3. The method of claim 2 wherein said tobacco is injected into saidconduit at a rate of from about 300 to 900 pounds per hour.

4. The method of claim 2 wherein said menthol and tobacco are conveyedtogether through said conduit downstream from the injecting of saidmenthol to provide sufficient contact between the menthol and tobacco.

